Any of the ones that have the triangle cutting edge in the middle - you can use it to make mini toasties for parties by turning the sandwich after 1 minute - cuts it into 4 minis!
I would recommend buying a George Forman instead of a sandwich maker. I find the sandwich maker squashes the sandwiches and all the cheese is pushed out, then it gets stuck to the trays of the sandwich maker.
This happens a bit with the GF sometimes but I find it's not as much and it's also much easier to clean.
Then again, I have a very old Morphy Richards Sandwich maker, maybe sandwich making technology has improved since then!
Would you believe but there was a recent post on "How to clean your George Foreman?".... you won't need to remove the plates - wipe it clean when warm - no scraping or soaking!
I have just spotted the "how to clean posts". Since submitting my original post I was enjoying a toasted sandwich at my friend's house and when she had finished making the goodies she switched off the appliance, put a wet tea towel on the grill, closed it and let it "cook" away. Said it made cleaning much easier. So now I have some cleaning options.